Wave and tidal energy:

Waves and tides are another source of energy which is perpetual and can be converted into electric energy, particularly where sea water can move into a narrow cut, such as is provided naturally where rivers flow into the sea. Energy carried by water has also been widely used in India's hilly  regions, since a wheel with pedals can be made to turn when  it is put  in a fast flowing strehm. Flour mills of  small size built on this principle were used  in Kashmir for long time. In fact, large "hydroelectric" power stations work on the same principle. A natural or artificial water fall is made to turn a modem kind of pedal wheel, called a turbine, which  rotates and causes electricity to k  generated.